Don't know if anyone has used Penofin's product:
Marine Oil Finish | Penofin
I built some decks on my house back in Mass using clear mahogany, and used their product on my decks, and it was fantastic.
I've never used the marine product, but based on my previous experience with their products, I'd give it a shot, especially given it's UV protection.
Maybe someone here has used it, and will chime in...